1. Field of the Invention
The present invention relates to an image forming apparatus that forms color images.
2. Description of the Related Art
Among image forming apparatuses such as printers, copiers, and all-in-one machines, those provided with a color printing mode and a monochromatic mode have been known. Further, a full-color mode and a two-color color mode are known as color printing modes.
In the full-color mode, printing is performed using all of the color toners provided in the image forming apparatus, and in the two-color color mode, printing is performed using a black toner and one chromatic color (specific color) other than black. A chromatic color is obtained by mixing a plurality of chromatic color toners.
In the above-described image forming apparatus, the two-color color mode is implemented in the below-described manner.
The above-described image forming apparatus is provided with a plurality of color component counter units having, for example, blue, green, and red color components allocated one by one thereto. Each color component counter unit counts the number of pixels of the color allocated to the color component counter unit from among a plurality of pixels included in image data.
Then, the above-described image forming apparatus sets the color corresponding to the color component counter unit with the highest count value as the specific color (one specific color). The image forming apparatus then prints the black portions of the image data with black and prints the color portions by using the specific color that has thus been set.
In business documents, black characters constitute a major portion of the document, and only a logo mark, which is a company mark, is often printed in a chromatic color. This is because the color of the logo mark is an important element representing the company. Further, only underlining lines and markers in the black text document are also often printed in a chromatic color.
Since the logo mark color is often the corporate color representing the specific company, the user needs this logo mark color to be truthfully reproduced on the paper. It is also desirable that the underlining lines and markers be truthfully reproduced.
The following problems are encountered when a document in which only a pattern such as a logo mark, underlining lines, and markers are printed in a chromatic color is printed in a two-color color mode in the above-described image forming apparatus.
Thus, since the above-described image forming apparatus prints the color portion by using the color corresponding to the color component counter unit with the highest count value, the color that can be used for printing the color portion is limited to any of the colors that have been allocated to the color component counter portions in advance.
For this reason, even when the original color image that is to be printed uses only one color other than black, a difference in hue can occur between the color of the color portion in the original color image and the color of the color portion actually printed in the two-color color mode.